根据文件的url在网络上下载文件url.openConnection()

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 URL url = new URL("http://127.0.0.1:8080/cfStruts2Ex2/");
 URLConnection urlConn = url.openConnection();

 System.out.println("Date: " + new Date(urlConn.getDate()));
 System.out.println("Content-Type: " + urlConn.getContentType());

 int length = urlConn.getContentLength();
 System.out.println("Content-Lentgth: " + length);

 if (length > 0) {
     System.out.println("========== Content ==========");
     InputStream input = urlConn.getInputStream();

     int i = length;
     int c;
     while ((c = input.read()) != -1 && --i > 0) {
         System.out.print((char) c);
     }
     input.close();
 } else {
     System.out.println("No Content.");
 }